Disposable lids are generally employed in connection with disposable plates, platters, bowls and the like items; perhaps most typically such plates, platters and bowls are made of paper, plastic or foil. Since it is highly desirable to make disposable lids as lightweight as possible, lid rigidity and especially crush-resistance are frequently product issues. Likewise, while it is desirable to have a leak-proof seal between a container base and lid, the seal geometry must be such that the lid can be easily secured to the base and easily removed without spillage or undue effort. The present invention containers and lid have a variable engagement profile in order to achieve these ends. Before turning to a discussion of the invention, the following patents are noted.
U.S. Pat. No. 6,733,852 to Littlejohn et al. discloses a disposable serving plate with a sidewall-engaged sealing cover. In a preferred construction a plate includes a substantially planar central area, a plate sidewall extending outwardly and upwardly from the central area, a recessed sealing area and a container base stop ridge adjacent the sealing area. A convex outwardly extending rim adjoins the base stop ridge and has an outer lip or border formed thereabout. A resilient mating domed lid is fitted to the plate.
U.S. Pat. No. 6,440,509 also to Littlejohn et al. discloses a compartmented disposable plate with asymmetric rib geometry. The three compartment, disposable serving plate includes three ribs in an asymmetric array angularly joined to the bottom and sidewall of the plate. The plate exhibits remarkable strength and is preferably thermoformed from a plastic material such as mica-filled polypropylene.
Other art related to compartmented containers, including covered and disposable compartmented containers includes the following: U.S. Pat. No. 5,915,581 to Pfirrmann, Jr. et al.; U.S. Pat. No. 3,107,027 to Hong; U.S. Pat. No. 3,633,785 to Cyr et al. Of the foregoing patents, U.S. Pat. No. 5,915,581 is perhaps of particular interest. The '581 patent discloses a two-piece container including a plate having a peripheral rim and a cover with a peripheral flange. The flange of the cover has a rim portion adapted to overlappingly engage the rim of the plate in a releasable interlocking relationship. To facilitate alignment of the cover and the plate an indexing protrusion is configured to engage an indexing cut out of the cover. The cover has a top wall provided with a depending divider for defining compartments corresponding to compartments of the plate. Still further art relating to compartmented containers includes the following United States Patents: U.S. Pat. No. 3,303,964 to Luker, U.S. Pat. No. 3,938,688 to Ryan; U.S. Pat. No. 4,874,083 to Antoni et al. and U.S. Pat. No. 6,595,366 to Brown.